Abstract: Macromolecular Crystallography Core The aim of the macromolecular crystallography (MX) core is to provide access to, and support for the use of, world-class beamlines for MX. There are two MX beamlines supported through this core, the first is the Highly Automated Macromolecular Crystallography beamline (AMX) (17ID-1), a tunable, high flux microbeam where we have placed an emphasis on automation of the experiments. The second beamline, Frontier Microfocusing Macromolecular Crystallography (FMX) (ID17-2) offers a high-flux x-ray beam with dimensions tunable from 1 to 10 micrometers, and the software and hardware to support the use of this resource. The success of the resources depends on access, support during experiments, and training of the users in the use of our beamlines. We assure merit-based access through a peer-reviewed process run by the National Synchrotron Light Source II (NSLS-II). To meet the needs of the community we have developed multiple access types that allow science-driven prioritization of access to the largest number of principal investigators. The review of experiments is performed by the independent Peer Review Panel (PRP), who generate a documented ranking and critique for every project submitted by users for each access mode. In addition, the PRP provide regular feedback on the performance and future direction of the beamlines. We provide support for the users of our resource firstly by interaction to discuss their experimental plan, and secondly by training of the scientists and their co-workers to use the instruments. We achieve reliable operation by applying performance standards for our instrumentation, and by performing scheduled preventive maintenance. Each experiment is assigned a ?local contact,? the first point of contact for training and support, who is responsible for liaison before, during, and after each experiment. We have a team of seven PhD-trained crystallographers, and several are cross-trained to operate both AMX and FMX. To aid efficient use of the two beamlines we have developed common controls software for the experiments and common hardware when possible. This provides multiple benefits: three different groups of workers need know only one set of controls ? the beamline scientists, the visiting users, and the equipment-support engineers and staff. We have a plan to continue the development of the NSLS-II MX beamlines at the leading edge of the technology available. The developments fall into three areas: the optical components that provide the x-ray beams, the hardware and software for performing diffraction experiments, and continued improvements of our data- analysis software and hardware. Beamline instrumentation developments include deploying a multi-layer monochromator to increase brightness, new sample-delivery formats to increase throughput, and new pipelines to improve data handling. Our instrumentation will be improved to allow for more efficient handling of microcrystals and delivery of samples into the beamline by a variety of methods: injectors, high density micro supports and in-situ examination of samples.